The compression of medium and high molecular weight gases within a small bore reciprocating compressor often presents some troublesome and unique problems. Since these gases require a larger flow area than lighter gases, a design which incorporates this perimeter often requires a larger more costly cylinder. In addition to providing a certain gas flow area into and out of the valve, it is also necessary to provide a valve which will withstand minor quantities of liquid on the valve seat. Minor amounts of liquid cause the valve disc or plate to impact into the stop for the valve on opening, and on closing, a single drop of liquid on the seat appears as a hard lump to the valve disc with subsequent bending of the disc. The ability of the valve to continuously seal while being subjected to the above action, should ensure a long useful service life.
Attempts heretofore to reduce the impact forces in opening and closing of the valve have been attempted through dampening of a valve plate or disc. This dampening is achieved by either trapping gas behind the valve disc or plate to provide a gas cushion for the plate to impact into or providing a second plate loaded with a spring force.
Heretofore, no valves have allowed passage of gas on both sides of an annular valve ring which has a short stroke to limit the problems which occur on impacting a droplet of moisture on the valve seat or behind the valve.